1. Field of the Invention
This invention relates to an assembly for embossing a decorative pattern on at least one surface of a thermoplastic, synthetic material, particularly of the type used to form elongated vertical slats in a vertical blind assembly.
2. Description of the Prior Art
Elongated vertically oriented slats of the type used in vertical blind assemblies are of course well known in the art and commercially available in a wide variety of designs. The formation of such slats usually occurs through a forming machine such as but not limited to an extruder, forming an elongated continuous slat from a hot melt thermoplastic material.
One problem well recognized in this industry is the formation of the decorative pattern on at least one exposed surface of the vertical slat. Attempts have been made in this industry and in other areas to emboss a specific decorative pattern or like indication at least one exposed surface through the utilization of cooperative pairs of rollers engaging opposite surfaces of an elongated thermoplastic material. In such a known prior art application, one of the rollers has a roughened or otherwise specifically formed exterior surface which is continuously forced into confronting engagement with an exposed surface of the slat. The prior art procedure involves that transferring of the decorative pattern or like indicia from the exterior surface of the one roller to the confronted surface of the elongated thermoplastic strip being formed.
One well recognized problem in the vertical blind industry is the fact that the slat issues from the extruder or like forming machine in a somewhat semi-rigid state due to such material being formed at an increased temperature of approximately 340 degrees Fahrenheit to 365 degrees Fahrenheit. Obviously, this temperature may vary depending upon the particular method of formation and the thermoplastic material being used. Upon completion of the elongated slat, and after cooling it is in at least partially rigid state because it is greatly reduced in temperature. When so cooled, the amount of pull or driving force which may be applied to the slat can be in the range of normally 300 pounds per square inch. However, due to the increased temperature and the semi-rigid state of the slat as it issues from the forming machine, it is generally accepted that less that three pounds of "pull" can be exerted on the slat. While this is beneficial from the standpoint of forming or "embossing" a decorative pattern or like indicia on at least one exposed surface, it raises the problem of adequately forcing the elongated slat through the forming rolls in order to accomplish such preferred embossing.
The problem is compounded by the fact that the overall configuration and dimension of the slat is such as to be defined by a somewhat curvilinear cross-sectional configuration or "profile". In addition, the width or transverse dimension of the slat, after formation from the extruder, is substantially in the range of 31/2 inches wherein the width ranges from 28/1000 of an inch to 31/1000. It is therefore seen that while the strip may be of adequate width to properly handle, the thinness of the slat presents a difficulty which adds to the problem of adequately embossing one or both surfaces of the elongated slat.
Again, it is recognized that prior art attempts have been made to emboss one or more exposed surfaces of an elongated thermoplastic, synthetic material slat or strip. Such prior art procedures are generally disclosed in the following U.S. patent.
The patent to Guy, U.S. Pat. No. 4, 600,461 is directed towards an apparatus and process for producing an extruded plastic material product which is specifically indicated as consisting of an inner foamed thermoplastic cellular core and an outer nonporous thermoplastic skin extending along one side of the core the product is formed, at least in part from an extrusion machine. After exiting the dye outlet a film of nonporous material is applied along the extruded foamed material. It is important to note that rollers are engaging in opposite sides of the extruded product primarily for purposes of adhering the outer skin to the foamed product. There is specifically no indication of a pulling force being exerted on the formed product by positively driven rollers and it is questionable whether such is possible or intended by Guy since the strength of the material and its degree of rigidity is not clearly indicated as in the subject invention to be described in greater detail hereinafter.
The patent to Funakoshi et al, U.S. Pat. No. 4,111,626 is directed to a compacting machine utilizing a pair of opposed, compressing rollers associated with the material as it exists a hopper type of structure.
The patent to Johnston, U.S. Pat. No. 4,289,470 is directed to a lasagna noodle rippler machine and shares the use of opposing roles with some type of indented or recessed configuration apparently for purposes of shaping the cross sectional configuration of the resulting product.
The patent to Wittkopf, U.S. Pat. No. 4,591,757 discloses a multi-role calendar apparatus including 5 rollers mounted in a common horizontal plane wherein at least some of these roles are heated or otherwise temperature regulated the heated rollers or rolls include an outer finished surface which for purposes explained in detail are provided to imprint some type of design pattern on the resulting product.
The Shigemoto, U.S. Pat. No. 4,880,589 is specifically directed to process of the use of two cooperative rollers wherein the formed strip passes through the nip of the rollers and has one of its sides forced into engagement with a roughened exterior surface on one of the rolls.
The patent to Baus, U.S. Pat. No. 4,615,090 discloses a forming tool for the production of sheets including thermoplastic, synthetic material wherein the tool comprises a roller, a press or a casting mold and further wherein specific material are "blown" or forced into the nip of the forming roll to add to the configuration of the exposed surface or surfaces of the sheet being formed.
The patent to Schulz, U.S. Pat. No. 4,803,032 is directed to the embossing of a sheet of non-woven, fibrous web material such as toilet tissue with a series or identical embossed elements arranged in a uniform pattern in a manner to avoid nesting of the embossments and a resulting non-uniform product.
While the techniques, apparatus and procedures disclosed in the above-noted patents are believed to be operative and functional for their intended purpose, none address themselves to the specific formation of an embossed, decorative surface on at least one exposed surface of an elongated thermoplastic, synthetic material slat prior to cooling such slat wherein the thickness and transverse dimensions of the slat as well as the material from which it is formed are specifically applicable to use of such a slat in the vertical blind industry.